For increasing the whiteness of highlights (hereinafter, are referred to as Dmin) of lamination layer integral type color diffusion transfer photographic elements, various investigations such as, for example, the improvement of silver halide emulsions and dye-providing materials, and the addition of hydroquinones, etc., have hitherto been made. An attempt at capturing dyes unnecessary for images by adding a dye mordanting quaternary ammonium salt or a polymer thereof to a light-shielding layer of a diffusion transfer photographic element is proposed in U.S. Pat. Nos. 3,788,855, 3,898,088, etc.
The foregoing attempt may provide a large improvement effect but the attempt of further improving Dmin by the technique disclosed in the above-described patents causes a reduction of other photographic properties (e.g., reduction of maximum density, reduction of sensitivity, etc.) and hence the technique disclosed in the foregoing patents is unsuitable for a composite system of a lamination layer integral type color diffusion transfer photographic element.
Carbon black itself is oleophilic and an attempt at rendering carbon black hydrophilic by graft polymerizing carbon black with a polymer is disclosed in Japanese Patent Application (OPI) Nos. 147561/80, 81038/74, etc. (the term "OPI" indicates an unexamined published patent application open to public inspection). However, since the graft compound is usually obtained as a solution in ethanol or an ethanol/water solvent or is frequently dissolved in an aqueous ammonia solution at use, such a graft compound is not used for diffusion transfer photographic elements. Also, if a solvent such as ethanol is removed from the solution of the graft compound obtained in the foregoing techniques for using the graft compound for diffusion transfer photographic elements, the graft compound obtained by removing the solvent shows poor dispersibility in water and thus if such a graft compound of carbon black is used in the light-shielding layer, etc., of a diffusion transfer photographic element, the surface-smoothness of the coated layer containing the graft compound and uniform dispersion of the graft compound in the coated layer are reduced, whereby the light-shielding function which is the desired object of blackening the layer becomes insufficient.
The conventionally known graft compound obtained by grafting carbon black to a polymer as described above is unsuitable for diffusion transfer photographic elements.